I think this is two bugs, one that the dutch word Wachtwoordcodevergrendeling is very long for "Passcode lock", and the other that once the localized string is too long, the cropped string overlaps with the control.
Ton, can you shorten the passcode lock string, maybe by strongly relying on teh context and just dropping half of the word?

This is probably one of a number of strings that “are too long”. I have not checked the entire source for them yet, as I don’t trust the emulator (of which the Windows version is still broken), based on the font settings.
‘Wachtwoordcodevergrendeling’ can be considered as the only proper translation, and nobody likes to shorten strings because of too little room for them. Nevertheless, I wanted to change this to ‘Vergrendelen met wachtwoordcode’ - this would need 2 lines, which apparently isn’t possible. I don’t like to change wording or switch the word order in compound words and change their meaning either, so ‘Vergrendelingscode’ is not a real option. Therefore I chose to shorten it to ‘Codevergrendeling’ - this fits in the emulator.
https://hg.mozilla.org/gaia-l10n/nl/rev/e992a14dfa1d
As I wrote in some other bug (and I don’t want to sound moody), I’d like to point out that IMO any developer of any web page or program capable of using more languages than just English should realize his/her design should not be ‘just big enough to make English strings fit’. Instead he/she should have clear understanding of the fact that English is a very compact language, its compound words may use spaces where others may not, and string lengths are generally longer for non-English locales, like appx. +20% for Dutch, German, and probably even more for Italian, Spanish etc. (Ever divided the size of a non-English text file size by the size of an English one?) This ‘design rule’ would save localizers lots of trouble, as well as developers their efforts to use CSS or other tricks, mostly afterwards.
As I’m about to leave for an estimated week in hospital after surgery, feedback may appear a bit low. Feel free to discuss other options or close the bug if satisfied, this string will remain on my radar anyway. ;)